Mailing List lml@lancaironline.net Message #34871
From: <Sky2high@aol.com>
Sender: <marv@lancaironline.net>
Subject: Nathan's Peeve Clarified
Date: Mon, 13 Mar 2006 21:08:01 -0500
To: <lml@lancaironline.net>
In a message dated 3/11/2006 10:30:57 P.M. Central Standard Time, marv@lancaironline.net writes:
In addition to making the proper calls and no more to avoid frequency
congestion, how about those who operate with their transponders on while on
the ground creating lots of TA's on those airplanes equipped with TCAS. I know
guys that turn the TCAS off when close to an airport- just when you probably
need it most.  When I break out on an IFR approach and find that the TA's that
have been sending my pucker factor off the chart are from someone sitting on
the taxi-way it makes me want to go over and yank his transponder right out of
the panel. Collision avoidance is everyone's responsibility; even when you are
only on the ramp you are creating a safety hazard if you have your transponder
on. (you cause others to turn off or disregard TCAS). There is a section in
the AIM about this too.  You can call this Nathan's pet peeve if you like.
Nathan,
 
AIM 4.1.19 Transponder Operation
a. General
......
3. Civil and military transponders should be adjusted to the "on" or normal operating position as late as practicable prior to takeoff and to "off" or "standby" as soon as practicable after completing landing roll, unless the change to "standby" has been accomplished previously at the request of ATC. IN ALL CASES, WHILE IN CONTROLLED AIRSPACE EACH PILOT OPERATING AN AIRCRAFT EQUIPPED WITH AN OPERABLE ATC TRANSPONDER MAINTAINED IN ACCORDANCE WITH 14 CFR SECTION 91.413 SHALL OPERATE THE TRANSPONDER, INCLUDING MODE C IF INSTALLED, ON THE APPROPRIATE CODE OR AS ASSIGNED BY ATC. IN CLASS G AIRSPACE, THE TRANSPONDER SHOULD BE OPERATING WHILE AIRBORNE UNLESS OTHERWISE REQUESTED BY ATC.
............
6. It should be noted by all users of ATC transponders that the coverage they can expect is limited to "line of sight." Low altitude or aircraft antenna shielding by the aircraft itself may result in reduced range. Range can be improved by climbing to a higher altitude. It may be possible to minimize antenna shielding by locating the antenna where dead spots are only noticed during abnormal flight attitudes.

7. If operating at an airport with Airport Surface Detection Equipment - Model X (ASDE-X), transponders should be transmitting "on" with altitude reporting continuously while moving on the airport surface if so equipped.

...........

Note the apparent conflict in 3.  TCAS shouldn't notice non-responding transponders where antennas are hiding under the ground plane and there is no radar originated request seen below certain altitudes (see 6).  However, if you are unsure of ASDE at your instant location, leave the dang thing on.

BTW, since my traffic detector can't give me azimuth, I just turn it off near an airport destination and rely on the big sky theory.

How about a modern, positive solution -- Like my Garmin 430 that doesn't record flight data until 30 Kts ground speed is exceeded, the same logic could be used to activate/deactivate a transponder set to "auto" for fixed wing aircraft not on a ADSE equipped airport.  Choppers could use rotor speed. 

Gee, I hope all those LSAs are Mode C equipped.....

 
Scott Krueger AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)
 
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